A turbo-charged internal combustion engine is understood to be an internal combustion engine with an exhaust gas turbo-charger. An exhaust gas turbo-charger is mainly composed of a turbine disposed in an exhaust system of the internal combustion engine and a compressor disposed in the intake system of the internal combustion engine, which are both connected together via the drive shaft. The turbine is driven by the exhaust gas flow of the internal combustion engine, and for its part, drives the compressor via the drive shaft, by means of which the combustion air of the internal combustion engine is compressed, thereby increasing the charging pressure of the internal combustion engine. This leads to increased cylinder filling, and with it, to increased performance of the internal combustion engine. Therefore, the performance of an existing internal combustion engine can be increased in a relatively simple manner by means of an exhaust gas turbo-charger. Likewise, the pollutant emissions of an internal combustion engine of a specific engine-power class can be reduced by using a smaller, i.e. smaller cylinder capacity basic engine, in conjunction with an exhaust gas turbo-charger.
With the use as a drive motor in a motor vehicle, however, the frequent changes of engine speed negatively affect the operating behavior of a turbo-charged internal combustion engine. It is particularly disadvantageous that in the case of the driver requesting, through an appropriate actuation of the gas pedal, an increase of the engine performance at low engine speeds, initially the internal combustion engine must be accelerated above the boost threshold speed so that due to an increased exhaust gas flow, the compressor of the exhaust gas turbo-charger is driven by the turbine with such an increased rotational speed, so that an increased charging pressure is generated, thereby resulting in the desired increase in engine performance. The effect of the exhaust gas turbo-charger begins only above the boost threshold speed.
Below the boost threshold speed, a spontaneous increase of the engine torque and with it the engine performance is possible only up to an intake torque that the internal combustion engine can generate in the intake operation maximally for a short period, i.e. without an increase of the charging pressure by the exhaust gas turbo-charger. This functional interaction is particularly evident in a delayed response during start-up and acceleration procedures of such a motor vehicle and a relatively low engine power of the internal combustion engine, which is generally designated as turbo lag.
This effect can also have negative impact during sudden upshifting when the speed of the internal combustion engine during a shift, for matching the coupling speed, is reduced so far that after completion of the shift, due to a reduced speed of the compressor of the exhaust gas turbo-charger, the charging pressure is so low that at the end of the shift, a significantly reduced engine power of the internal combustion engine is available, and with it a lower ability to accelerate the motor vehicle.
To avoid or at least mitigate the undesired turbo lag in the past, multiple solutions were proposed and some were even implemented, such as an adjustable turbine geometry for improving the response behavior of the exhaust gas turbo-charger, or auxiliary devices for increasing the charging pressure at low engine speed, for instance a mechanically drivable compressor, an electrically drivable supplemental compressor, or a mechanical or electrical drive of the drive shaft of the exhaust gas turbo-charger. Such devices are, however, relatively complex and expensive, increase the construction space requirements and represent increased failure potential for the operation of the internal combustion engine, so that they are frequently omitted.
Due to the effects of the dynamic operating characteristics of a turbo-charged internal combustion engine on the entire drive train, these must be considered particularly with the control of the start-up and shift procedures. With the use of an automated stepped transmission, such as an automatic transmission that can be connected to the drive shaft of the internal combustion engine by means of a single automated friction clutch, or an automated double clutch transmission that can be alternately connected to the drive shaft of the internal combustion engine by means of two friction clutches, specific control procedures, such as determining the start-up gear and the drive speed with a start-up procedure, determining the shiftable gears in an incline, and the control of a friction clutch during the start-up and drive shifting procedures, thus depend also on the load build-up potential of the respective internal combustion engine, generally designated as a response behavior.
Because applicable information is not immediately available, i.e., cannot be transmitted by an engine control device of the internal combustion engine to the transmission control device of the stepped transmission via a data line or a CAN data bus, the dynamic operational characteristics of an internal combustion engine have up to now been considered only implicitly with the clutch and shift control of an automated stepped transmission, that is, by a corresponding design of the associated characteristic maps and characteristic curves for controlling the stepped transmissions. This procedure is, however, disadvantageously connected with a high coordination effort, which is necessary again even with a minor change of the engine characteristics of the internal combustion engine, which can result for example from adapting the engine control to tighter exhaust gas limit values.